A centering device of the pre-cited type known from DE 43 00 612 A1 comprises a spring element in the form of a metal folding bellows which is connected at one end to an end element which is fixed on the drive shaft. The other end of the metal folding bellows is connected to a centering element. The centering element which is axially spring-mounted through the metal folding bellows presses through rolling elements against a second centering element which is fixed on an end element. This end element connects the torsion bar to the driven shaft. The fact that the rolling elements roll in angular grooves of the centering elements results in the production of a resetting force which is determined by the relative rotation of the two shafts and is added to the torsional force of the torsion bar. A centering device of this type effects an exact adjustment of the two shafts, and thus also of the steering valve, at the hydraulic center. This prior art centering device is suitable for rotary slide or rotary piston structures and assures a perfect straight-ahead driving behavior.
A drawback of the above construction, however, is that the spring element in the form of a folding bellows is expensive to manufacture and its connection to the centering element and the torsion bar is work-intensive and thus also involves high costs.